Some cavalierly refer to IP telephony as "just another application" that rides over your data network. But wait and see what happens if VoIP call quality starts eroding or, worse yet, if your organization's phone calls stop altogether.
In this Clear Choice Test, we evaluated a burgeoning class of new products, collectively called VoIP analysis tools. These wares help the VoIP network manager proactively monitor and troubleshoot the IP telephony environment to ensure call continuity.
Seven vendors accepted our invitation: Agilent Technologies, Brix Networks, ClearSight Networks, Fluke Networks, Touchstone Technologies, Viola Networks and WildPackets.
ClearSight's Analyzer garnered the Network World Clear Choice award for its extreme ease of use and its capability to analyze a range of VoIP protocols. Fluke's OptiView package made a strong second-place showing by capturing a substantial amount of information on the VoIP calls. However, it was a bit more tedious to use. There was a near-three-way tie for third place between Agilent, Touchstone and WildPackets, all of which provided much more complete analysis of VoIP traffic in the Session Initiation Protocol (SIP ) environment than proprietary environments.
We found - and users also need to keep in mind - that VoIP analysis tools are oriented toward particular VoIP protocol environments. Interpreting different call-control-protocol sequences is difficult because the messages vary considerably with the particular protocol used.
We tested each package in four different VoIP environments over a two-month period (see "How we did it" ). Using this methodology, we tested the packages against three proprietary protocols and with two SIP-based implementations.
The tools tested dramatically differ in their abilities to monitor and track SIP standards-based VoIP activity compared to how they work in proprietary protocol environments. Only two of the products, ClearSight's Analyzer and Fluke's OptiView package, did a good job tracking all VoIP activity in both standard-based SIP and proprietary-protocol VoIP environments.
But other products tested - such as Agilent's combination of Distributed Network Analyzer MX (DNA MX) probe and Telephony Network Analyzer (TNA) software and WildPackets' EtherPeek VX - still can view parts of VoIP phone traffic in different protocol environments. This is because actual VoIP conversations follow a fairly standard format across protocol environments. They comprise bidirectional Real-Time Transport Protocol (RTP) over User Datagram Protocol (UDP ) streams, which are fairly easy to spot and decipher using tools that recognize RTP streams even if the IP PBX uses a proprietary signaling protocol.
The tools we tested mostly are specialty PC-based software applications. Many are add-ons to the vendors' network data analyzer, which provide the ability to recognize and process IP-telephony call control and VoIP conversations.
Long-time test-and-monitor vendor Agilent addresses VoIP monitoring through Real-Time Transport Control Protocol and RTP monitor applications that integrate with its popular Network Analyzer package. Its VoIP analysis package can be based on a laptop, run off a mirrored switch port or run on a probe appliance inserted in-line in key backbone network segments. We tested Agilent's 100M bit/sec capacity DNA MX probe that can fit with almost any network interface type, handle Gigabit links at wire speed and be accessed remotely from anywhere on the network. We ran the TNA software on a separate PC that communicated with the DNA MX over the network.
We ran ClearSight's software-only Analyzer on a Windows XP laptop. It sniffs passing traffic and captures all the packets traveling on the network, then analyzes them for VoIP traffic and associates the VoIP packets with the proper conversation. The network analyst's laptop usually is situated on a mirrored switch port to watch traffic that's copied and redirected from key traffic links.
Fluke's OptiView package can run on a PC or on a special probe designed for in-line insertion on a backbone link and is based on packet-sniffing data capture and analysis. We tested it with a Gigabit-capacity in-line probe that cost about $21,800. We also ran it on a Windows 2000 laptop via a mirrored switch port. The VoIP analysis software was the same in both configurations, but the separate-probe approach is better suited to multi-site distributed environments.
Another implementation based on packet sniffing is Touchstone's software-only product, WinEyeQ, which we ran on a Win 2000 PC as it watched passing traffic on a mirrored switch port. WinEyeQ seems to be more focused on VoIP traffic than its packet-sniffing competitors because all of the screens in Touchstone's product were specifically designed for VoIP analysis.
WildPackets' EtherPeek VX is also Windows-based software and is a packet-sniffing monitor tool, which we ran on a Win 2000 PC, on a mirrored-switch-port connection.
Brix's BrixMon relies on hardware probes called verifiers that generate simulated VoIP traffic based on canned tests that you can tailor to your network. This test traffic is sent between verifiers. Brix says the system can monitor and report on real VoIP traffic, but we found it difficult to get this feature to work properly in the different scenarios.
Viola's NetAlly is a software-only package that also issues simulated streams of VoIP traffic sent between its distributed PC clients.
With simulated traffic there is no direct observation or monitoring of real user's VoIP traffic, therefore both BrixMon and NetAlly are indifferent to VoIP protocols. This can be useful if you plan to use the tool in a pre-deployment phase of an IP PBX system to assess if the current network infrastructure can perform adequately for VoIP traffic. But then, when real VoIP traffic is implemented on the network, you don't get the same level of VoIP-level protocol detail and real traffic analysis that the other packages provide.
In this category, our top marks went to Agilent and Fluke in large part because of the additional deployment topologies and options they support. The BrixMon system was notably much more difficult to deploy and get working properly.
Real-time VoIP monitoring
Our test is weighted heavily toward how well these products assist the process of real-time VoIP monitoring. Our assessment is based on whether information could accurately be reported in the following areas:
• VoIP call control (that is, call initiation and setup signaling).
• Status of current VoIP calls.
• Details about current VoIP calls (caller destination, vocoder used, etc.).
• Bandwidth consumption by current VoIP calls.
• IP addresses of key VoIP nodes and endpoints (call controller, gateways, IP phones).
• Latency, jitter and packet loss, for VoIP calls between two distributed sites.
The tools that offer real-time information turned in the best results, by far,when monitoring SIP-based VoIP activity. WildPackets did the best job, in part, because of its slick, graphical, state-based, SIP call-progress display. ClearSight was a close second, offering the same amount of real-time information. However, it wasn't as easy to determine which calls were completed. Agilent, Fluke and Touchstone all did a fairly good job tracking SIP-based call control.
Viola offers little in terms of in real-time monitoring and analysis of SIP or proprietary VoIP environments. Brix generates simulated VoIP protocols streams, too, like Viola, but also can monitor user VoIP streams to some extent.
When you turn to tracking proprietary call-control environments, ClearSight was the hands-down winner. In addition to the half-dozen VoIP protocols it formally supports, ClearSight categorized calls based on other proprietary protocols as generic call control. Fluke, which we placed second in this regard, did a good job tracking the proprietary call-control protocols, which classified them as "unknown" call control. ClearSight displayed the key VoIP parameters on one screen, where Fluke required additional windows to view all the parameters associated with a VoIP call.
How about tracking and reporting of VoIP calls? In the SIP environment, WildPackets had the best showing because you can click on a VoIP call and bring up a well laid-out display window showing a jitter graph, the server name, the IP addresses or the endpoints, and other call information. Agilent's tool set was also noteworthy. It displayed the VoIP calls on a tabular screen with the call information spread across the columns of the table.
Fluke and Touchstone reported similar information, but we felt it was more difficult to navigate the screens to view the data with these tools. ClearSight presented the VoIP statistics in a large table making it a bit tedious to find key VoIP parameters.
For call monitoring in proprietary-protocol environments, ClearSight and Fluke turned in good performances by still presenting all the VoIP call information. WildPackets and Agilent did an adequate job monitoring proprietary-protocol calls because of their general data-analysis capabilities, but none of the others could effectively display VoIP call information in proprietary environments.
The ability to report VoIP bandwidth consumption was also split along protocol lines. ClearSight did the best job accurately reporting VoIP bandwidth and other VoIP-activity details such as jitter, latency and packet loss in both the SIP and proprietary environments. Fluke was a close second here, effectively reporting VoIP details in all protocol environments but not as elegantly as ClearSight.
Based on SIP traffic only, Touchstone, Agilent and WildPackets all did an excellent job analyzing VoIP call control and reporting call performance statistics.
Across all protocols, Fluke did the best job monitoring and reporting key QoS conditions. ClearSight, Viola and Brix also did well monitoring QoS in all protocol environments, but there were some cases in which all information was not reported consistently. Brix and Viola reported QoS conditions based on their own generated traffic and were not sensitive to the actual VoIP control protocol used by the IP PBX.
In standard SIP-only environments, WildPackets and Fluke did the best job reporting network impairments and QoS-type conditions consistently and accurately. All other products displayed the QoS parameters, but, in some cases, the values were not reported consistently.
Clean and legible
It's not enough for a VoIP analysis tool to accurately track the information you seek,it must also let you readily locate the data, and view it in a clear, straightforward manner. In this critical area of usability and navigability, these products varied considerably.
ClearSight placed first. All its VoIP data and measurements come from applets launched from one screen. VoIP streams are shown in a log-type table. The user selects any one and drills down for more detail. The graphics are all clean and very legible. A summary tab shows totals for bandwidth and flows. There's a single click to capture and play back any VoIP stream.
WildPackets was close behind (see graphic ). EtherPeek VX's interface does a great job distinguishing closed VoIP calls from active calls, which is useful in conducting diagnostics. It's easy to see who is on the phone in real time. Another WildPackets' plus is a very slick peer map feature, a dynamic, graphical representation of real-time flows and connections.
As long as you are working with either SIP or H. 323 protocol streams, Touchstone's interface is refreshingly simple to navigate. A single, well-organized VoIP screen provides seven tabs for individual applets. Everything is structured on a VoIP call-by-call basis; it is easy to capture, trace, record and delete calls.
Agilent's interface provides volumes of technical details, but finding only the data you want can be tedious. The main VoIP display is somewhat awkward to use, and on-screen help could be more, well, helpful.
Fluke's OptiView system can run in monitor or capture mode, and it's difficult to tell which is running at any time. However, the output is different depending on the mode and we found this a constant nuisance. Like Agilent, the wealth of captured data available to the user is impressive. It's just a little complex to find what you're after. The newer set of VoIP applications - including VoIP Properties, Call and Channel Details - are easier to use and navigate than the older data analyzer base of the system, such as Capture Views, Network Monitoring and Expert Views.
The interface and data displays for Viola's NetAlly - while limited to information collected in its simulated tests - are all clean and clear. Brix's package is focused on generating simulated VoIP streams as part of programmed tests, akin to Viola. The Brix user interface is consistent for the various tests, but it takes time to become familiar with the screen navigation techniques using hyperlinks and various buttons.
Besides real-time VoIP monitoring, we set aside some test criteria to address any additional, useful reporting capabilities.
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